We form coronas of serum proteins on gold nanorods (NRs) coated with cetyltrimethylammonium bromide (CTAB). These coronas can be exploited for their ability to hold small molecular therapeutics at a capacity much higher (~5-10×) than what covalent conjugation strategies can achieve. Coronas are loaded with DNA oligonucleotides and Doxorubicin, showing that they can hold species of either negative or positive charge. Payload capacity varies with assembly strategy, ionic strength, and loading concentration. Payload release can be achieved by increasing the temperature or by ultrafast laser excitation of the NRs at their longitudinal surface plasmon resonance. DNA leakage from the corona is minimal within the first 3 days of preparation, although Dox leakage was more significant. The coronas also stabilize the NRs in buffer and biological media. This study demonstrates the biological utility of the protein corona around nanomaterials, contrasting the common view of the corona as an undesirable biological response.

Our study shows a facile two-step method which does not require the use of core templates to load a hydrophobic photosensitizer drug chlorin e6 (Ce6) within polydopamine (PDA) nanoparticles (NPs) while maintaining the intrinsic surface properties of PDA NPs. This structure is significantly different from hollow nanocapsules which are less stiff as they do not possess a core. To our knowledge, there exist no similar studies in the literature on drug loading within the polymer matrix of PDA NPs. We characterized the drug loading and release behavior of the photosensitizer Ce6 and demonstrated the therapeutic efficacy of the combined photodynamic (PDT) and photothermal therapy (PTT) from Ce6 and PDA, respectively, under a single wavelength of 665 nm irradiation on bladder cancer cells. We obtained a saturated loading amount of 14.2 ± 0.85 μM Ce6 in 1 nM PDA NPs by incubating 1 mg/mL dopamine solution with 140 μM of Ce6 for 20 h. The PDA NPs maintained colloidal stability in biological media, whereas the pi-pi (π-π) interaction between PDA and Ce6 enabled a release profile of the photosensitizer until day 5. Interestingly, loading of Ce6 in the polymer matrix of PDA NPs significantly enhanced the cell uptake because of endocytosis. An increased cell kill was observed with the combined PDT + PTT from 1 nM PDA-Ce6 compared to that with PTT alone with 1 nM PDA and PDT alone with 15 μM equivalent concentration of free Ce6. PDA-Ce6 NPs could be a promising PDT/PTT therapeutic agent for cancer therapy.

We manipulate the passive release rates of DNA payloads on protein coronas formed around nanoparticles (NPs) by varying the corona composition. The coronas are prepared using a mixture of hard and soft corona proteins. We form coronas around gold nanorods (NRs), nanobones (NBs), and carbon nanotubes (CNTs) from human serum (HS) and find that tuning the amount of human serum albumin (HSA) in the NR-coronas (NR-HS-DNA) changes the payload release profile. The effect of buffer strength, HS concentration, and concentration of the cetyltrimethylammonium bromide (CTAB) passivating the NP surfaces on passive release is explored. We find that corona properties play an important role in passive release, and concentrations of CTAB, HS, and phosphate buffer used in corona formation can tune payload release profiles. These advances in understanding protein corona properties bring us closer toward developing a set of basic design rules that enable their manipulation and optimization for particular biological applications.

We load Ce6 onto NRs using its protein corona, deliver them to cells before performing laser irradiation for simultaneous PTT and PDT with greatly enhanced therapeutic efficacy.

A direct process for preparing contiguous gold shells (15−25 nm thick) over amorphous silica spheres (200 nm) is described. In this method, gold seeds are synthesized from HAuCl4 in a dilute NaOH solution using deposition−precipitation with subsequent metallization by sodium borohydride (NaBH4). The ease of dispersing gold nanocrystals on spheres of bare silica and spheres after grafting with ammonia was studied as a function of pH (4−8), reaction temperature (65−96 °C), and time (5−30 min). Additional parameters requiring optimization included the quantity of NaBH4 and the HAuCl4 in K2CO3 solution to silica volume ratio. The evolution of gold nanocrystal growth was monitored by transmission electron microscopy, and the bathochromic shift of ultraviolet−visible absorption was correlated with shell perfection and thickness.

Understanding heat dissipation processes at nanoscale during cellular thermogenesis is essential to clarify the relationships between the heat and biological processes in cells and organisms. A key parameter determining the heat flux inside a cell is the local thermal conductivity, a factor poorly investigated both experimentally and theoretically. Here, using a nanoheater/nanothermometer hybrid made of a polydopamine encapsulating a fluorescent nanodiamond, we measured the intracellular thermal conductivities of HeLa and MCF-7 cells with a spatial resolution of about 200 nm. The mean values determined in these two cell lines are both 0.11 ± 0.04 W m−1 K−1, which is significantly smaller than that of water. Bayesian analysis of the data suggests there is a variation of the thermal conductivity within a cell. These results make the biological impact of transient temperature spikes in a cell much more feasible, and suggest that cells may use heat flux for short-distance thermal signaling.

The stability of gold nanorods (NRs) coated with amphiphilic ligands (ALs) was investigated. NRs coated with cetyltrimethylammonium bromide (CTAB) were ligand exchanged with polyoxyethylene [10] cetyl ether (Brij56), Oligofectamine (OF), and phosphatidylserine (PS). An aggregation index based on the longitudinal surface plasmon resonance peak broadening was used to measure stability of the NR-ALs under different conditions including the number of washes, pH, ionic concentration, and temperature. The aggregation index was also used to measure the stability of the NR-ALs under ultrafast laser irradiation and in the presence of proteins commonly used in cell culture. Differences in NR-AL stability were found, which were due to differences in the physical and chemical properties of the ALs. Apart from the charge on the AL headgroup, we suggest the Gibbs free energy of passivation (ΔG(p)) and enthalpy of passivation (ΔH(p)) of the AL could potentially aid in the selection of amphiphiles that can effectively passivate NRs for stability and optimize their properties and desired biological impact.

The one-pot seedless protocol provides a facile approach in the synthesis of gold nanostars (AuNS) that involves only three reagents, gold (III) chloride (HAuCl 4 ), silver nitrate (AgNO 3 ) and ascorbic acid (C 6 H 8 O 6 ). While studies correlating the synthesis parameters of the seedmediated protocol to surface-enhance Raman scattering (SERS) enhancement is well reported, the same understanding of the one-pot seedless protocol is limited. Here, we aim to elucidate how the synthesis parameters of AuNS from the one-pot seedless protocol, the AuNS concentration, surface passivation and aggregation level affect the colloidal SERS enhancement. Using crystal violet (CV) as a Raman probe molecule, we found that the SERS enhancement increases with Au 3+ /C 6 H 8 O 6 molar ratio up to 0.60 and Au 3+ /Ag + molar ratio up to 18. Although the surfactant, cetyltrimethylammonium bromide (CTAB) maintained colloidal stability, it reduced the SERS enhancement. Interestingly, the SERS enhancement did not increase monotonically with AuNS concentration, but decreased when AuNS concentration was beyond 15 pM. The SERS enhancement also increased with the increasing level of salt-induced aggregation of AuNS, but only within a few minutes. While the concept of SERS with colloidal nanostructures is not new, we have shown for the first time, a detailed systematic study of various parameters that affect the SERS enhancement of AuNS synthesized using a one-pot seedless protocol. This study enables us to optimize the SERS enhancement of AuNS at the synthesis level to make them effective colloid-based SERS substrates for potential use in intracellular biosensing.